Advanced, high-performance engines will require main shaft bearing compartment seals with improved performance relative to conventional seals, while also being required to meet more aggressive cost, weight, size, and reliability metrics. Improved capability main shaft bearing compartment carbon seals are needed to meet the increased demands of next generation high-performance engines. Carbon seals enable an engine and bearing compartment to function with minimal impact on Thrust Specific Fuel Consumption (TSFC), a thermal management system (TMS), and a lubrication system.
Advanced aircraft engines require seals with improved wear resistance, improved performance, and improved reliability in order to meet customer, user, or program metrics. Conventional applications have experienced elevated wear and sealing dam breakage, which results in an increase in air leakage and oil loss characteristics. Excessive seal housing coning slope in the divergent direction, with respect to an air flow direction, contributes to additional axial contact pressure and carbon element wear. Excessive seal housing coning slope in the divergent direction increases the axial air load and resulting contact pressure. For applications that contain excessive levels of housing coning slope, elevated shaft speeds, air pressure differential, small contact area and existing high levels of contact pressure, existing environments would introduce significant risk for axial carbon wear issues and life concerns.
FIG. 1A illustrates a typical seal environment as would be known to one of skill in the art and includes one or more carbon rings 1 (arranged adjacent to one another in FIG. 1A), radial springs 2, axial springs 3, and/or seal housings 4 placed atop/proximate a seal runner 5. Referring to FIG. 1B, one of the carbon rings 1 is shown in an unworn condition. In contrast to FIG. 1B, due to axial carbon ring wear during operational use, a wear “step” 1′ may be created as shown in FIG. 1C.